Pipe A can fill the tank 3 times faster than pipe B . If both pipes A and B can fill the tank in 36 minutes running together, find how much time will pipe A take to fill the tank alone ?

48 min

The correct answer is option (2) : 48 min

Let pipe A take x min to fill the tank alone, then pipe B will take 3x min to fill the tank alone.

So, part of tank filled by pipe A in 1 min $=\frac{1}{x}$

Part of tank filled by pipe B in min $=\frac{1}{3x}$

Given both pipes A and B together fill the tank in 36 min

$∴\frac{1}{x}=\frac{1}{3x}=\frac{1}{36}$

$\frac{4}{3x}=\frac{1}{36}$

$x= 48$

Hence the time by pipe A to fill the tank alone is 48 min